The need for filtering water for use, drinking, and consumption to remove impurities has long been recognized. The traditional method of purifying water is, of course, to pass the water through a water treatment facility. Such purified water is, however, often unavailable for persons engaged in international travel and for persons traveling through the back country. Although water may macroscopically appear clean and pure, it may nevertheless contain such impurities as bacteria, pesticides, Giardia and other Protozoa. For backpackers and persons traveling abroad, it is also desirable that the filter be small and easily portable, yet capable of separating such impurities from water drawn from a body of water, such as a lake or stream.
There are, however, several problems associated with traditional portable water filters. One problem relates to the intake of water into the water filter. There may be times when it is desirable to draw water from a body of water at a particular depth where the water is the purest. If, for example, a layer of scum lies on the top of a body of water, it may be desirable to place the opening of the intake hose several inches to several feet below the surface to filter the best quality of water available. This will lengthen the life of the filter and improve ultimately the quality of water obtained. Alternatively, if the most contaminated water resides close to the bottom of a body of water, it may be desirable to adjust the depth of the opening of the intake hose so that it is located close to the surface.
Another problem with respect to the intake of water into the water filter relates to dynamic bodies of water. In rivers and streams, the opening of an inlet hose on the filter may bob up and down in the water and remain, at least momentarily, above the surface of the water which prevents drawing a full stream of water into the intake hose.
Yet another problem associated with typical portable water filters is the large contaminants and objects that are suspended in the body of water from which water is being drawn. Absent a preliminary means for filtering the water before it enters into the intake hose, the valves and pumping mechanism can be damaged and the filter rendered useless in a relatively short period of time. Prescreening is thus desirable where relatively large foreign objects, such as twigs, leaves, heavy sediment or other large-sized objects, may be present in the water to be filtered.
Traditional prefiltering methods involve a variety of types of filters and screens. While these prefilters prevent large obstacles from entering into the intake hose, they are commonly permanently attached to the end of the intake hose and thus require backflushing to clean the prefilter and free it of objects that have become lodged in the filtering pores.
Still another problem associated with traditional portable water filters relates to clogging of the main filter medium within the filter body. Once the main filter medium has become clogged, which is inevitable over the long run, the filtering (usually carried out by some manner of pumping) becomes progressively more difficult. In most pump models, for example, the water discharged from the outlet remains the same for each full stroke of the piston being pumped. The more clogged the filter medium, the more difficult it is to pump. This increased difficulty of filtering water requires more effort for each pumping stroke, which also increases the strain on the parts and the operator. This pressure build-up within the filter also places additional stress on the mechanical parts, which can lead to failure of these parts.
Relief valves have heretofore been looked upon with disfavor in conjunction with small, portable water filters because of the added complexity to the water filter. A separate discharge tube is generally required to direct the pressurized water being relieved outside the filter.
Another problem associated with conventional portable water filters involves the mechanical means for forcing water through the filter. Prior filtering devices have included piston-cylinder arrangements where a rod is coupled to the piston so as to coincide with the orthogonal axis of the cylinder. The rod is typically secured in place relative to the cylinder by a wall with a central aperture through which the rod must pass. This keeps the plane of the piston perpendicular to the orthogonal axis of the cylinder at all times while the piston moves back and forth in the cylinder.
Prior filters with piston-cylinder arrangements are usually actuated by pumping the rod directly in and out of the cylinder as is done by a typical hand-held tire pump. This type of ergonomic pumping action is awkward and makes the overall process of filtering water complicated and difficult.
Lever-action pumps have traditionally not been used for portable water filters. Such lever-action pump handles require many linkage parts to ensure that as the piston is moved back and forth, it constantly remains in a plane perpendicular to the orthogonal axis of the cylinder. To achieve this constant perpendicularity with the lever-action handle, several linkage members are needed which increases the overall friction, number of parts that may fail or wear out, and the overall complexity of the filter device.
Still another problem associated with portable water filters relates to the filter medium on the inside of the water filter itself. Over time, the filter medium will become clogged with the filtered impurities. Therefore, it is inevitable that the filter of the medium must be changed or backflushed in some way. Removal and replacement of filter mediums on traditional portable water filters is generally complicated and expensive.
A further problem exists with respect to damage to the filter element from impact resulting from, for example, dropping the filter. Water filters have traditionally lacked the ability to absorb shock to prevent damage to the filter medium. Carbon, a filter medium commonly used in portable water filters, is particularly susceptible to breakage upon impact.
There are also problems associated with the build up of impurities inside the filter, which may later be discharged from the filter. For example, carbon filters are commonly used in portable water filters to filter bacteria and other microscopic impurities from the water. Once used, some water will remain inside the carbon filter medium. The water that remains in the carbon filter medium may act as a breeding ground for bacteria. When this occurs toward the downstream end of the carbon filter, the water initially discharged after a long period of non-use may be contaminated with living organisms.
Some other problems associated with portable water filters involve the vessel into which the filtered water is placed for use. Traditionally, portable water filters have been cumbersome and awkward in their pumping.